Fouling-release Properties Research Articles

Characterization of Buried Interfaces of Silicone Materials in Situ to Understand Their Fouling-Release, Antifouling, and Adhesion Properties.

Poly(dimethylsiloxane) (PDMS) has numerous excellent properties and is extensively used as the main component of many silicone products in a variety of research fields and practical applications such as biomedical materials, aviation, construction, electronic devices, and automobiles. Interfacial structures of PDMS and other components in silicone systems are important for such research and applications. It is difficult to probe interfacial molecular structures of buried solid-liquid and solid-solid interfaces of silicone materials due to the lack of appropriate analytical tools. In this feature article, we presented our research on elucidating the molecular structures of PDMS as well as other additives in silicone samples at buried interfaces in situ at the molecular level using a nonlinear optical spectroscopic technique, sum frequency generation (SFG) vibrational spectroscopy. SFG was applied to study various PDMS surfaces in liquid environments to understand their fouling-release and antifouling activities. SFG has also been used to study buried solid-solid interfaces between silicone adhesives and polymers, elucidating the molecular adhesion mechanisms. Our SFG studies provide important knowledge on interfacial structure-function relationships of silicone materials, helping the design and development of silicone materials with improved properties through optimization of silicone interfacial structures.

Carp-inspired self-regulating marine antifouling coating: Featuring robust controlled release of eugenol and high-efficiency self-healing performance

The practical application of low surface energy polydimethylsiloxane (PDMS) in marine antifouling is significantly limited due to its inadequate static antifouling capability. Herein, integrating a strategy inspired by carps to release antifouling agents with the fouling release properties of low surface energy materials, an innovative self-regulating marine antifouling coating (named PDMS-Pun-x) was developed, which demonstrates remarkable robust ability of controlled release of eugenol and efficient self-healing performance. Under seawater, the coating regulates its inherent hydrophilicity and the content of the surface anti-fouling agent to obtain the ability of controlled releasing eugenol. Compared with other self-renewal coatings, there proves non-heavy metal leaching and no internal self-hydrolysis existing. Moreover, based on the synergistic action of disulfide bonds and hydrogen bonds, the coating demonstrated a notable self-healing performance, with a self-healing rate of 94.06%. Additionally, the substrate of PDMS modified with polyurea provides the coating with excellent resistance against corrosion. This study introduces a highly promising approach towards the advancement of environmentally-friendly and durable marine antifouling coatings.

Amphiphilic Balance: Effect of the Hydrophilic-Hydrophobic Ratio on Fouling-Release Surfaces.

This study demonstrated the importance of identifying the optimal balance of hydrophilic and hydrophobic moieties in amphiphilic coatings to achieve fouling-release (FR) performance that surpasses that of traditional hydrophobic marine coatings. While there have been many reports on fouling-release properties of amphiphilic surfaces, the offered understanding is often limited. Hence, this work is focused on further understanding of the amphiphilic surfaces. Poly(ethylene glycol) (PEG) and polydimethylsiloxane (PDMS) were used to create a series of noncross-linked amphiphilic additives that were then added to a hydrophobic-designed siloxane-polyurethane (SiPU) FR system. After being characterized by ATR-FTIR, XPS, contact angle analysis, and AFM, the FR performance was evaluated by using different marine organisms. The assessments showed that the closer the hydrophilic and hydrophobic moieties in a system reached a relatively equalized level, the more desirable the FR performance of the coating system became. A balanced ratio of hydrophilicity-hydrophobicity in the system at around 10-15 wt % of each component had the best FR performance and was comparable to or better than commercial FR coatings.

Preparation and Study of Antifouling and Fouling-Release Surface Materials from Copolymers with Anchoring Functional Groups

Marine biofouling is a worldwide problem in marine systems. Nowadays, innovative non-toxic antifouling and fouling-release materials are highly desirable. In this study, a strategy for preparing antifouling and fouling-release materials via one-step dip coating is reported. Copolymers were synthesized via the polymerization of a monomer with catechol sticky functional groups and four monomers with antifouling- or fouling-release functional groups, respectively. The copolymers could assemble onto different material surfaces, such as metals and plastics, using biomimetic catechol groups via multivalent complex bonding. The catechol groups were helpful for adhesion onto the surfaces, while the other functional groups endowed the coatings with antifouling or fouling-release properties. The effects of modifying the substrates using these copolymer coatings were verified via X-ray photoelectron spectroscopy; images of Chlorella cell and Ulva zoospore settlement were taken using a microscope and scanning electron microscope. The copolymer-coated surfaces, especially the surface modified by DOPA–PSPMA, displayed the best antifouling activity, and surface modification via DOPA–PTMETH was shown to be the most effective for producing the fouling-release property in the settlement assay.

Magnetically controlled interface weaving of dual-layer heterogeneous coatings with active and passive anti-corrosion protection

Polydimethylsiloxane (PDMS) elastomer exhibiting remarkable corrosion resistance and fouling release properties. However, their performances are often compromised due to the weak interfacial adhesion with rigid substrates. Herein, we have developed an innovative dual-layer heterogeneous coating via magnetic-controlled interface weaving technology, achieving a seamless integration of PDMS with a rigid epoxy (EP) substrate. Magnetic nanoparticles (Fe3O4@MPDA-MBT) were strategically incorporated into the coating system, guided by a magnetic field to facilitate their interfacial migration. This controlled migration of nanoparticles resulted in the formation of interface layer between the EP primer and PDMS topcoat, leading to a sharp increase in PDMS adhesion strength (3.0 MPa), which is over 7 times greater than that of control counterpart (0.4 MPa). Additionally, Fe3O4@MPDA-MBT were selectively enriched adjacent to the metal substrate, thereby endowing the coating with outstanding corrosion resistance, due to the quick releasing of enough MBT inhibitors, as confirmed by electrochemical tests with high corrosion resistance value (2.2 × 108 Ω·cm2). Also, the topcoat PDMS enabled the dual-layer heterogeneous coating to achieve fouling-release and cavitation resistance.

Transparent amphiphilic silicone-based fouling-release coatings: Analyzing the effect on coating-fouling interfacial behavior

The amphiphilic antifouling coatings are effective for inhibiting fouling adhesion. Herein, the amphiphilic coatings were prepared by introducing polyether-modified polydimethylsiloxane (PE-PDMS). Uniform morphology, high transmittance, low surface roughness and amphiphilic property were obtained. PE-PDMS appearing as interspersed chains endowed the coating with amphiphilic characteristic. The artificial seawater promoted the migration of polyether to the surface. The protein adhesion force and quality were significantly reduced according to AFM-based colloidal probe technique and Quartz Crystal Microbalance with Dissipation, respectively. The coating exhibited antibacterial activity against Pseudoalteromonas xiamenensis (84.0%), Escherichia coli (69.2%) and Staphylococcus aureus (63.0%), respectively. 63.1% Halamphora. sp and 75.8% Nitzschia closterium f. had been inhibited, while the coatings possessed outstanding fouling release property with above 76.1% diatom detached after water exposure, proving that the amphiphilic parts weakened the adhesion of fouling. The mussel settlement assay confirmed that less adhesive plaques existed over the amphiphilic coatings. In addition, the expression for mussel adhesion proteins (mfp-5 and mfp-6) were significantly increased, demonstrating that amphiphilic polymers interfered with the adhesion response of the mussels. The effect on the interfacial behavior between fouling and coating is explored, providing a meaningful issue for the development of environmentally friendly antifouling coatings.

Fabrication of antifouling UiO-66 nanofiltration membranes via surface fluorination engineering

Membrane fouling is a primary hindrance in the efficient utilization of nanofiltration technology in wastewater treatment, which increases energy requirements and reduces membrane life. In this work, a highly antifouling UiO-66 nanofiltration (NF) membrane was fabricated via a facile surface engineering for dye rejection, where fluoromonomer with a long fluoroalkyl chain was fast UV-polymerized on the surface of UiO-66. Fluoroalkyl chains have low surface energy and provide the surface with non-stick and fouling-release properties, and fluoroalkyl is highly incompatible with dyes. Meanwhile, the bridged rigid fluoroalkyl produces an effective barrier to repel the foulants because of the narrowed pore structure and smooth surface. Results showed that the resulting membrane shows an excellent NF performance including high rejection of Methyl Blue, Cango Red and Chrome Black T (all over 99.7 %) with a high water permeance of 249.6 L m2 h−1 bar−1, and salt permeation of MgSO4 (89.26 %) and NaCl (99.02 %). The long-term stability testing exhibits basically stable performance for separating the CT/NaCl mixture. The outcome of the work offers an effective strategy to solve the membrane fouling and maintain the outstanding separation performance by fluorination modification. This newly UiO-66-based NF membrane showed excellent application potential in the dye wastewater treatment.

Coatings to Reduce Fouling in Plate Heat Exchangers: Two Case Studies

Fouling of heat exchangers in the chemical industry, oil & gas industry, district heating, power plants, among others, results in a loss of performance which leads to production stops for cleaning and therefore increased operation costs. One approach to mitigate fouling is to alter the properties of the metal surface. A coating to be successful in any plate heat exchanger (PHE) application needs to have a good adhesion to the metal but also keep the heat transfer through the metal plates as unaltered as possible. This requires a thin coating with a relatively good thermal conductivity. The plates in a PHE are subjected to plate-to-plate contact point wear when in operation which also puts an extra requirement for the coating. To be suitable, the coating needs to have a good mechanical stability to resist this plate-to-plate wear. Alfa Laval has a long experience in coating plates for diverse applications and in this paper two case studies will be presented. One in the paper industry and the other in the biofuel industry. A new type of multilayer Teflon™ coating from Chemours was used, specifically designed to show excellent fouling release properties along with limited thicknesses (30–50 microns).

Cicada wing-inspired artificial nanopatterns with antifouling properties for clay adhesion

To clarify the antifouling properties of cicada-inspired nanostructured surfaces and search for a long-term usable antifouling material, the wings of two types of cicadas in Japan, Graptopsaltria nigrofuscata (GN) and Cryptotympana facialis (CF), were examined by surface wettability and surface free energy. Furthermore, considering the complexity and mechanical stability of natural nanostructured surfaces, we mimicked both cicada wing surfaces by combining nanosphere lithography and metal-assisted chemical etching (MacEtch) on Si wafer, which is low-cost and large-area pattern-fabricable. We obtained artificial nanopatterns with pillar pitches of 200, 500, and 1000 nm (naming 200, 500, and 1000 series). As a result, comparing artificial nanopatterns with cicada wings indicated that nanopillar structures with high roughness factors or structural aspect ratios are likely to have excellent hydrophobic properties and antifouling features. Cryptotympana facialis wings and 200 series Si samples showed less clay particle adhesion than other patterns. These results indicate smaller structured surfaces where air may get trapped, resulting in hydrophobic surfaces contributing to self-cleaning or fouling-release properties. Further, reducing the contact area between nanostructures and clay can be used as an effective strategy to prevent clay adhesion has been proposed, but it has targeted limitations. Herein, we present a novel insight that more fine and high-structural-density nanostructural patterns are universal to prevent clay adhesion.

Mechanically robust antifouling coating with dual-functional antifouling strategy by infiltrating PDMS into plasma-sprayed porous Al2O3-Cu coating

Marine biofouling is a worldwide challenge that needs to be solved urgently. Poly(dimethylsiloxane) (PDMS)-based fouling release coatings with low surface free energy (SFE) could effectively inhibit biofouling. Nevertheless, their poor mechanical durability, adhesive strength, and antifouling performance under static conditions significantly limit their applications. Herein, a novel mechanically robust Al2O3-PDMS-Cu composite coating with strong adhesive strength and remarkable antifouling performance was developed. The Al2O3-PDMS-Cu coating loaded with a small amount of Cu was fabricated by infiltrating PDMS into plasma-sprayed micro/nano-scaled porous Al2O3-Cu coating. Results showed that the fabrication of this Al2O3-PDMS-Cu coating did not alter the surface hydrophobicity and SFE of PDMS significantly, thus presenting little influence on its inherent fouling release property. After rigorous abrasion test, the Al2O3-PDMS-Cu coating presented remarkably improved surface hydrophobicity due to the exposure of micro/nano structure, rather than falling off as that of PDMS coating. The combination of excellent abrasion resistance and one order of magnitude higher adhesive strength and hardness than PDMS coating contributed to the outstanding mechanical robustness of Al2O3-PDMS-Cu coating. Additionally, the antifouling assays against marine bacteria adhesion (95% reduction rate for Escherichia coli. (E. coli)) and algae attachment (96% and 94% reduction rates for Chlorella and Phaeodactylum tricornutum (P. tricornutum), respectively after 21 days of incubation) demonstrated the superior antifouling performance of the Al2O3-PDMS-Cu coating. Thus, a high-performance Al2O3-PDMS-Cu antifouling coating with excellent mechanical robustness and long-term antifouling performance was achieved via the combination of mechanical durability of Al2O3 skeleton and the dual-functional antifouling strategy, i.e., the fouling release property of PDMS and fouling resistance of Cu.

Polyurethane coatings modified by OH-PDMS for anti-cavitation, antifouling and anticorrosion applications

Cavitation, biofouling, and seawater corrosion are important factors that reduce the service life of propellers and other overcurrent components of ship. Herein, OH-PDMS was introduced into polyurethane and a series of hydrophobic polyurethane coatings (SiPU-X) with anti-cavitation, antifouling and anticorrosion functions were synthesized by a simple addition reaction. The chemical composition and microstructure of the prepared coatings were analyzed by means of FT-IR, SEM, and EDS, and it was found that the addition of OH-PDMS enhanced the degree of microphase separation of SiPU-X. The addition of OH-PDMS resulted in a large number of island structures of OH-PDMS on the coating surface. The SiPU-15 with the optimal microphase separation had better tensile strength of 12.33 MPa, excellent hydrophobicity (with a contact angle of 105.3°), hydrolysis resistance (with a hydrolysis rate of 0.26 %), and water repellency (with a water absorption of 2.21 %). More importantly, the weight loss (7.1 mg) of SiPU-15 was much lower than that of SiPU-0 (10.0 mg) under 60 h cavitation owing to the suitable microphase structure on the surface. In addition, SiPU-15 exhibited excellent fouling release properties and could remain in the ocean for 60 days without microbial adhesion. The |Z|0.01Hz of SiPU-15 can maintain 3.33 × 107 Ω·cm2 after immersion in 3.5 wt% NaCl for 10 days. This work provides a heuristic perspective on the design of polymer materials with cavitation, fouling, and corrosion resistance performance.

Nitroxide-Containing Amphiphilic Random Terpolymers for Marine Antifouling and Fouling-Release Coatings

Two types of amphiphilic random terpolymers, poly(ethylene glycol methyl ether methacrylate)-ran-poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate)-ran-poly(polydimethyl siloxane methacrylate) (PEGMEMA-r-PTMA-r-PDMSMA), were synthesized and evaluated for antifouling (AF) and fouling-release (FR) properties using diverse marine fouling organisms. In the first stage of production, the two respective precursor amine terpolymers containing (2,2,6,6-tetramethyl-4-piperidyl methacrylate) units (PEGMEMA-r-PTMPM-r-PDMSMA) were synthesized by atom transfer radical polymerization using various comonomer ratios and two initiators: alkyl halide and fluoroalkyl halide. In the second stage, these were selectively oxidized to introduce nitroxide radical functionalities. Finally, the terpolymers were incorporated into a PDMS host matrix to create coatings. AF and FR properties were examined using the alga Ulva linza, the barnacle Balanus improvisus, and the tubeworm Ficopomatus enigmaticus. The effects of comonomer ratios on surface properties and fouling assay results for each set of coatings are discussed in detail. There were marked differences in the effectiveness of these systems against the different fouling organisms. The terpolymers had distinct advantages over monopolymeric systems across the different organisms, and the nonfluorinated PEG and nitroxide combination was identified as the most effective formulation against B. improvisus and F. enigmaticus.

Fouling Resistance and Release Properties of Poly(sulfobetaine) Brushes with Varying Alkyl Chain Spacer Lengths and Molecular Weights

We examined the effects of alkyl carbon spacer length (CSL) and molecular weight on fouling resistance and release properties of zwitterionic poly(sulfobetaine methacrylate) brushes. Using surface-initiated atom transfer radical polymerization, we synthesized two series of brushes with CSL = 3 and 4 and molecular weight from 19 to 1500 kg ·mol-1, corresponding to dry brush thickness from around 6 to 180 nm. The brush with CSL = 3 was nearly completely wet with water (independent of molecular weight), whereas the brush with CSL = 4 exhibited a strong increase in water contact angle with molecular weight. Though the two-brush series had distinct wetting properties, both series of brushes exhibited similarly great resistance against fouling by Staphylococcus epidermidis bacteria and Aspergillus niger fungi spores when submerged in water, indicating that neither molecular weight nor CSL strongly affected the antifouling behavior. We also compared the efficacy of brushes against fouling by fungi and silicon oil in air. Brushes grafted to filter paper were strongly fouled by fungi and silicon oil in air. Grafting the polymers to the filter paper, however, greatly enhanced removal of the foulant upon rinsing. The removal of fungi and silicon oil when rinsed with a salt solution was enhanced by 219 and 175%, respectively, as compared to a blank filter paper control. Thus, our results indicate that these zwitterionic brushes can promote foulant removal for dry applications in addition to their well-known fouling resistance in submerged conditions.

Antifouling graphene oxide membranes for oil-water separation via hydrophobic chain engineering

Engineering surface chemistry to precisely control interfacial interactions is crucial for fabricating superior antifouling coatings and separation membranes. Here, we present a hydrophobic chain engineering strategy to regulate membrane surface at a molecular scale. Hydrophilic phytic acid and hydrophobic perfluorocarboxylic acids are sequentially assembled on a graphene oxide membrane to form an amphiphilic surface. The surface energy is reduced by the introduction of the perfluoroalkyl chains while the surface hydration can be tuned by changing the hydrophobic chain length, thus synergistically optimizing both fouling-resistance and fouling-release properties. It is found that the surface hydration capacity changes nonlinearly as the perfluoroalkyl chain length increases from C4 to C10, reaching the highest at C6 as a result of the more uniform water orientation as demonstrated by molecular dynamics simulations. The as-prepared membrane exhibits superior antifouling efficacy (flux decline ratio <10%, flux recovery ratio ~100%) even at high permeance (~620 L m−2 h−1 bar−1) for oil-water separation.

Silicone low surface energy antifouling coating modified by zwitterionic side chains with strong substrate adhesion

Silicone fouling release coatings were receiving increasing concern due to of their eco-friendly properties. However, their poor fouling resistance capability and mechanical properties limited the applications. Herein, we reported a type of silicone low surface energy coating with zwitterionic side chains and the carbamates group was introduced into the Si-O main chain. The carbamates groups and zwitterions provided strong substrate adhesion up to 2.0 MPa through hydrogen bond and ion interaction which also endowed the good mechanical properties higher than 6.0 MPa. The coating had a low surface energy less than 30 mJ·m−2, and exhibited good fouling release properties in the range of 0.3–0.5 MPa. Also, zwitterions gave the coating excellent fouling resistance properties. The bioassays showed that the anti-bacterial efficiency of PDMS-zPDEM-14 coating against Pseudomonas sp. was 94.86%, the coating could inhibit the formation of biofilm (the coverage area was only 13.64%) and effectively prevent the adhesion of diatoms (the density of adhered diatoms was 107 cells/mm2) This work had promising applications in low surface energy marine antifouling coating and interfaces of biomaterials.

Design and Development of Fluorinated and Biocide-Free Sol-Gel Based Hybrid Functional Coatings for Anti-Biofouling/Foul-Release Activity.

Biofouling has destructive effects on shipping and leisure vessels, thus producing severe problems for marine and naval sectors due to corrosion with consequent elevated fuel consumption and higher maintenance costs. The development of anti-fouling or fouling release coatings creates deterrent surfaces that prevent the initial settlement of microorganisms. In this regard, new silica-based materials were prepared using two alkoxysilane cross-linkers containing epoxy and amine groups (i.e., 3-Glycidyloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, respectively), in combination with two functional fluoro-silane (i.e., 3,3,3-trifluoropropyl-trimethoxysilane and glycidyl-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononylether) featuring well-known hydro repellent and anti-corrosion properties. As a matter of fact, the co-condensation of alkoxysilane featuring epoxide and amine ends, also mixed with two opportune long chain and short chain perfluorosilane precursors, allows getting stable amphiphilic, non-toxic, fouling release coatings. The sol–gel mixtures on coated glass slides were fully characterized by FT-IR spectroscopy, while the morphology was studied by scanning electron microscopy (SEM), and atomic force microscopy (AFM). The fouling release properties were evaluated through tests on treated glass slides in different microbial suspensions in seawater-based mediums and in seawater natural microcosms. The developed fluorinated coatings show suitable antimicrobial activities and low adhesive properties; no biocidal effects were observed for the microorganisms (bacteria).

Cu@C core-shell nanoparticles modified polydimethylsiloxane -based coatings with improved static antifouling performance

PDMS-based fouling release coatings have promising applications in the fields of marine fouling control. However, development of silicone-based coatings with good antifouling / fouling-release property under relative static conditions remains challenging. In this work, a new PDMS-based nanocomposite coating consisting of PDMS matrix and nanofiller of copper@carbon core-shell nanoparticles was developed. Uniformly dispersed Cu@C core-shell in the PDMS matrix enhance the antifouling ability. The PDMS with low surface energy endows the composite coatings with hydrophobicity thus fouling release property. The introduction of Cu@C core-shell/PDMS improves both the Young's modulus, tensile strength and the elongation at break. Furthermore, laboratory bioassay against diatom adhesion and field tests indicated that the PDMS-based nanocomposite coatings with Cu@C core-shell exhibited outstanding antifouling / fouling-release property even under static conditions, showing promising application in marine antifouling.

Poly(vinylidene fluoride)/partially alkylated poly(vinyl imidazole) interpolymer ultrafiltration membranes with intrinsic anti-biofouling and antifouling property for the removal of bacteria

Bacterial contaminated water causes potential health issues. Conventional chlorine treatment has shortcomings of environmental hazards and chlorine adoptability by the bacterial cells. Ultrafiltration membrane can intercept bacterial species from feed water. Membrane having anti-biofouling/antifouling properties is needed for the removal of bacteria from feed water. Herein, interpolymer membranes with inherent antimicrobial activity and fouling release property have been prepared by the blend of poly(vinylidene fluoride) (PVDF), poly(vinyl pyrrolidone) and partially long chain alkylated (C12 chain) poly(vinyl imidazole) copolymer (PVIm-co-PVIm-C12) followed by cross-linking of the remaining VIm groups with an activated di-halide compound. The membranes obtain with copolymers of degree of alkyl substitution (DSC12) in the range of 0.75–0.85 and amount in the range of 0.9–3.5% w/w in the casting solutions exhibit good antimicrobial activity (>99 % of inhibition) and dynamic anti-biofouling property. The membrane prepared with 0.9% w/w of the copolymer (DSC12=0.85) shows higher flux recovery ratio (91 % for bacterial filtration and 88 % for protein filtration) compare to a pristine membrane (57 % for bacterial filtration and 58 % for protein filtration). The membrane is able to reject the bacteria completely. Use of small amount of copolymer and facile fabrication of stable anti-biofouling/antifouling membranes show potential for the purification of bacterial contaminated water.

Fabrication of a Modified Polyethersulfone Membrane with Anti-Fouling and Self-Cleaning Properties from SiO2-g-PHEMA NPs for Application in Oil/Water Separation

To prepare anti-fouling and self-cleaning membrane material, a physical blending modification combined with surface grafting modification has been carried out; first, poly (2-hydroxyethyl methacrylate) grafted silica nanoparticles (SiO2-g-PHEMA NPs) were synthesized using surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and used as a blending modifier to fabricate a polyethersulfone (PES)/SiO2-g-PHEMA organic–inorganic membrane by the phase-inversion method. During the membrane formation process, hydrophobic PES segments coagulated immediately to form a membrane matrix, and the hydrophilic SiO2-g-PHEMA NPs migrated spontaneously to the membrane surface in order to reduce interfacial energy, which enhanced the hydrophilicity and anti-fouling properties of the PES/SiO2-g-PHEMA membrane. Importantly, the membrane surface contained abundant PHEMA segments, which provided active sites for further surface functionalization. Subsequently, the carboxyl-terminated fluorocarbon surfactant (fPEG-COOH) composed of hydrophilic polyethyleneglycol segments and low-surface-energy perfluorinated alkyl segments was synthesized via the esterification of fPEG with succinic anhydride. Lastly, the PES/SiO2-g-PHEMA/fPEG membrane was prepared by grafting fPEG-COOH onto surface of the PES/SiO2-g-PHEMA. Thus, a versatile membrane surface with both fouling-resistant and fouling-release properties was acquired. The PES/SiO2-g-PHEMA/fPEG membrane has a large oil–water flux (239.93 L·m−2·h−1), almost 21 times that of PES blank membrane and 2.8 times of the PES/SiO2-g-PHEMA membrane. Compared with the unmodified PES membrane, the flux recovery ratio increased from 45.75% to 90.52%, while the total flux decline ratio decreased drastically from 82.70% to 13.79%, exhibiting outstanding anti-fouling and self-cleaning properties. Moreover, the grafted fPEG segments on the membrane surface show excellent stability due to the presence of stable chemical bonds. The grafted segments remain at the surface of the membrane even after a long shaking treatment. This suggests that this PES/SiO2-g-PHEMA/fPEG membrane material has potential for application in oil/water separation.

Investigation of N-Substituted Morpholine Structures in an Amphiphilic PDMS-Based Antifouling and Fouling-Release Coating.

Biofouling is a major disruptive process affecting the fuel efficiency and durability of maritime vessel coatings. Previous research has shown that amphiphilic coatings consisting of a siloxane backbone functionalized with hydrophilic moieties are effective marine antifouling and fouling-release materials. Poly(ethylene glycol) (PEG) has been the primary hydrophilic component used in such systems. Recently, the morpholine group has emerged as a promising compact alternative in antifouling membranes but is yet to be studied against marine foulants. In this work, the use of morpholine moieties to generate amphiphilicity in a poly(dimethylsiloxane) (PDMS)-based antifouling and fouling-release coating was explored. Two separate coating sets were investigated. The first set examined the incorporation of an N-substituted morpholine amine, and while these coatings showed promising fouling-release properties for Ulva linza, they had unusually high settlement of spores compared to controls. Based on those results, a second set of materials was synthesized using an N-substituted morpholine amide to probe the source of the high settlement and was found to significantly improve antifouling performance. Both coating sets included PEG controls with varying lengths to compare the viability of the morpholine structures as alternative hydrophilic groups. Surfaces were evaluated through a combination of bubble contact angle goniometry, profilometry, X-ray photoelectron spectroscopy (XPS), and marine bioassays against two soft fouling species, U. linza and Navicula incerta, known to have different adhesion characteristics.